The present invention relates generally to outboard motors and other recreational products, and more particularly, to a molded silencer to reduce the transmission of engine noise beyond a housing positioned about the engine.
The present invention is applicable to both two-cycle, or two-stroke, and four-stroke engines. The combustion process of the engine generates noise that transfers, in part, directly through components of the engine. That is, during the combustion process, noise associated with the combustion, as well as the combustion impact on the internal surfaces in the combustion chamber, transfers through the engine components and is audible therebeyond. In addition to the noise that transmits through the components of the engine, engine noise can also exit the engine along the gas paths to and from the combustion chamber. That is, the air intake system provides combustion gas to the engine while an exhaust gas system provides the discharge path for the combustion process exhaust gases. Noise can carry on these gas paths and ultimately exit the engine. This noise is occasionally trapped in a volume of space between the engine and the housing and reverberates therein resulting in inadvertent amplification of the engine noise. Ultimately, the engine noise either transmits directly through the housing or exits the housing via openings therein.
Noise generated by an outboard motor, for example, can be a distraction to an otherwise well-performing engine. Additionally, a quieter operating engine that eliminates any noise is generally advantageous. Many efforts have been made to create a quieter operating engine. A muffler is often implemented on an exhaust side of an engine and air intake silencers have been implemented on an intake side of the engine to “muffle” noise transmitted along the gas paths to and from an engine. Additionally, attempts have been made to lessen the amount of general engine noise emitted directly through the housing positioned about the engine.
Known methods of silencing this general engine noise include positioning a rigid housing or cover about the engine with sound directing openings therethrough. These sound directing openings generally direct the noise of the engine away from an operator but do little to reduce the total amount of noise emitted from the motor. In an effort to further decrease the engine noise transmitted through the housing, foam inserts have been cut and glued into cavity spaces that exist between the components of the engine and the housing. This type of engine silencing is time consuming to implement and only marginally effective at silencing the general noise emitted from the engine. Additionally, over time, the foam inserts and the adhesives used to glue them into place can become damaged or degraded thereby reducing the ability of the foam inserts to attenuate noise.
It would therefore be desirable to have a system and method capable of more efficiently silencing an engine.